Collectors frequently come across .44 and .45 caliber cartridges with a .22 R.F. blank inserted backwards into the nose of a hollow point bullet. The problem is that the target has to be hard enough to detonate the explosive, and usually there is not enough blast ot be effective.

And my understanding is for really hard targets you want a bullet that penetrates more rather than expands more. So, best case scenario you'd wind up with a round that behaves like a HP against hard targets and like FMJ against soft ones? It sounds less than ideal.